A need has been identified for a service which will provide to residential customers a control over their telephone service to permit work or relaxation without the normal interruptions caused by a ringing telephone. Such a service must be easy to use, economically priced, and must provide courteous handling of incoming calls.
In recent years a do-not-disturb service has been commonly offered in PBX systems and has been proposed for central offices equipped with the more modern stored program control (SPC) electronic switches. Such switches are typified by the 1AESS and 5AESS electronic switching systems manufactured by American Telephone & Telegraph (AT&T) Corporation. See, for example, U.S. Pat. No. 3,826,876 to Gueldenphenning et al, issued July 30, 1974; U.S. Pat. No. 4,232,199 to Boatwright et al, issued Nov. 4, 1980; U.S. Pat. No. 4,720,848 to Akiyama, issued Jan. 19, 1988; and U.S. Pat. No. 4,878,240 to Lin et al, issued Oct. 31, 1989.
The Lin et al patent discloses an arrangement providing enhanced telephone services which include call screening with a do not disturb feature. To provide such services the Lin et al arrangement provides each subscriber with two telephone numbers. One number is the published number which is known to the telephone switch and is the number that the public would dial to reach the subscriber. The other number is known only to an adjunct which is provided for the switch. Incoming calls to the subscriber's published number are routed by the telephone switch (as through a call forwarding feature) to the adjunct where it is then routed through an additional programmable switch for the duration of the call. Based upon the services subscribed to by the called party and based upon the condition of his telephone line (i.e., answered, busy or not answered), the call is routed to the other adjunct known number of the called party. The adjunct then causes the ringing of the subscriber's telephone, or if call forwarding is activated, to ring the published number of the forwarding party in order to ring the telephone there. This arrangement involves a significant investment in sophisticated adjunct equipment and a basic change in the way switching is handled in a central office switching system.
Other forms of do-not-disturb service or substitutes therefor have been available using various types of customer premise equipment. See, for example, U.S. Pat. No. 3,226,489 to Grambsch, issued Dec. 28, 1965; U.S. Pat. No. 3,867,584 to Rengren, issued Feb. 18, 1975; and U.S. Pat. No. 3,673,339 to Korn, issued June 27, 1972.
Still other currently available options to telephone interruptions include telephone answering machines, answering services, and receiver off-hook. While each of these options provides some relief from unwanted telephone calls each also carries its own inherent disadvantages. Thus the receiver off-hook option tends to aggravate callers when they receive busy signals on repeated calls. Still further, the user must remember to replace the receiver and go back on-hook. Answering machines and other customer premise equipment options entail a relatively high equipment investment along with maintenance costs. Answering machines further do not eliminate an unwanted ringing telephone. Voice Mail also entails a ringing of the telephone before the call is transferred to the Voice Mailbox. Both answering machines and Voice Mailbox involve a feeling of obligations to return the calls.